Receiving system



Feb. 28, '1933.

O. BCJHM RECEIVING SYSTEM Filed Jan. 30, 1929 mm fuss N64576:?

Patented Feb. 28, 1933 UN ETE STATES PATIENT oi=r1cn OTTO BOI-IM, OF BERLIN, GERMANY, ASSIGNOR T0 TELECEUNKEN GESELLSOHAFT F'llR DRAHTLOSE TELEGRAPHIE, M. B. H., OF BERLIN, GER-MANY, A CORPORATION OF GER- MANY RECEIVING SYSTEM Application filed January 30, 1929, Serial No. 336,112, and in Germany March 31, .1928.

This invention relates to the reception of short wave signals, and more particularly to a method and means for the utilization of echo signals to aid in the reception of short wave signals.

in the reception of short waves antenna systems comprising reflectors may be employed, for the purpose of receiving radiations from a definite direction, and toscreen ofl' radiations from the opposite direction.

N ow, it has been found that in spite of the screening effect of a reflector, the antennae are excited more or less strongly also by waves coming from the opposite directiomand one particular kind of trouble in operation is due to the fact that not only the signal coming in from the regular direction of reception, but also the same signal after having passed around the earth in the opposite sense reaches the receiving point, and excites the receiving antenna. Indeed, it happens quiteoften that this retrogressive signal comes in with far greater strength than the direct signal, so that, even in a case where only a fraction of the retrogressive signal happens to excite the antenna, owing to the eflect of the reflector, the ensuing intensity may nevertheless be substantially stronger than the volume of the directly received signal. Now, the object of the present invention is to utilize for reception both the directly received as well as the retrogressive signal, and to incidentally di-- niinish such disturbances as are occasioned by the time-difference between the direct and the retrogressive signal.

According to the invention, two antennae or antenna systems are employed at the receiving station, each thereof being equipped with a reflector. But the reflector of one antenna system is mounted at the side opposite the place of mounting of the reflector of the other antenna system, while the receiver antennae of both antenna systems are connected with a joint receiving apparatus.

7 My invention is described more in detail in the following specification, accompanied by a drawing in which one form of my invention is schematically illustrated.

For a better understanding of the scheme, reference is made to the drawing. Let a be the wave arriving from one direction and Z) the wave carrying the same signal from the other direction. A1 is oneantenna or antenna system and is provided with a reflector R1,

while A2 is the other antenna system and is provided with a reflector R2, the reflectors 7 serving to make the, antennae unidirectional The two antennae are I surface, the receiver E-willbe acted upon simultaneously by the two antenna systems.

However, as a general rule the distance between the transmitter and the'receiver will be such that the distancein one direction is shorter than that in the other. Supposing that signal a comes in over the shorter route, then the same signal 6 will come in over the other route with some time lag. In order that then, the indicatorv may be influenced simultaneously by both signals, it is necessary to insert in the connecting wire between antenna A1 and the receiverE a means whereby the transmission of the signal .1s retarded,

and this by an amount oftime just equalling the time of delay in arrival at the receiving end of the signal I), compared with the arrival of signal (1. Referring to Figure l, the

said retarding means is diagrammatically shown and indicated by the rectangle V. The

same may consist, for instance, of'a time-lag orretarding relay or the like.

In order to explain the diminution of the disturbance by means of such an arrangement, we will assume thatthereflector allows I the passage of only one-tenth the intensity of i the retrogressive signal. Antenna then picks up intensity at and one-tenth of the disturbing intensity 6. Hence, in this customary scheme the stray or disturbing intensity or signal 6) may turn out substantially larger than intensity a of the direct signal. The second arrangement receives intensity v2') and the stray intensity a. Also in this system taken by itself the intensity of the retrogressive or stray signal may under certain circumstances, turn out far stronger than the direct signal. Now, if according to this invention both arrangements are combined in such a way that the time interval or difference between signals a and b is neutralized, the receiver will be acted upon by a signal strength a+b. The disturbing signals will then be a and 6, respectively, and they can never exceed the value (a-l-b). Hence, the disturbing intensity in thisinstance is always independent of the value of a and b, indeed, it will amount to only a fraction of the sum total of the two signal strengths.

I claim: Y

1. A receiving system, especially for short waves comprising two antennae or antenna systems, each of which is furnished with a reflector, the reflector of one of said systems being mounted upon a side opposite the reilector of the other system, said two antennae or antenna systems being associated with a joint receiver responsive to all of the signal energy collected upon the two antennae or antenna systems.

2. Areceiving system, especially for short waves, comprising two antennae or antenna systems, each of which is furnished with a reflector, the reflector of one of said systems being mounted upon a side opposite the re fle ctor of the other system, said two antenna: or antenna systems being associated by means of leads with a joint receiver responsive to all of the signal energy collected upon the two antennae or antenna systems, one of said leads between one antenna system and'the receiving apparatus containing means such as a retarding relay adapted to equalize the time shift or diflerence in phase of the signals arriving from the opposite direction.

OTTO BOHM. 

